Originally Posted by Brian Ratliff

This is what the little book the officer is carrying and the court system is for. You don't get into a slap fight with a participant of a vehicle crash, at the crash scene where emotions are high. The OP might have interpreted the situation wrong. There might have been extenuating circumstances. The crash participant was, perhaps, intimidated by this fellow off the street into running off, perhaps with injuries, and leaving his bike behind.

I have been a participant in a car/bike collision (me on the bike). I couldn't even think straight (just adrenalin, not head injury, fortunately) enough to get a witness name and number. I didn't know enough to ask for a full set of driver info (got just name and cell number; useless if the other participant refuses to cooperate - you cannot even sue in small claims court because there isn't enough info to serve the law suite). I really, really wish that someone had just called 911 as I was getting myself off the ground, and had a police officer run both me and the other participant through the correct procedure. As it was, no police came because none was summoned; there was no police report, I had no info from witnesses, and I didn't have enough to get $200 out of the driver (who was at fault - pulled out of a parallel parking spot into my path; I was positioned in the middle of the far left lane of a one way street ready to make a left turn).